108 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



and also in combination with glycuronic acid. To isolate the 

 phenols or to detect their presence, these sulphuric acid esters 

 must be decomposed. This is done by heating with hydro- 

 chloric acid. 



1. Detection in Horse-urine. The filtrate obtained in the 

 preparation of hippuric acid (see VII, page 105) is diluted to 

 200 cc., and 150 cc. distilled off. The distillate has the char- 

 acteristic odor of paracresol. It frequently contains some 

 benzoic acid in crystalline form. 



A part of the cresol may be used for the reactions, the rest 

 is made faintly alkaline with sodium carbonate solution and 

 shaken in a separating-funnel with a little ether, the ether 

 separated and evaporated: there remains a mixture of cresol 

 and a little phenol. 



2. Detection in Human Urine. Two hundred cubic centi- 

 meters of urine to which 50 cc. of hydrochloric acid have been 

 added are distilled until a small portion of the distillate no 

 longer gives any turbidity with bromine-water. If we wish 

 to detect very small quantities (in normal urine), 500 cc. of 

 the urine are first made alkaline with sodium carbonate solu- 

 tion and evaporated nearly to dryness, the residue treated 

 with one-fifth of its volume of hydrochloric acid and distilled 

 (J. Munk). 



Instead of the roundabout method of distillation we may 

 make use of a shorter procedure, which depends on the 

 hydrolysis by nitric acid and conversion into nitro com- 

 pounds. This method is used especially to decide the ques- 

 tion whether much of the carbolic acid used in the dressing 

 of wounds, etc., is absorbed. In this case a parallel experi- 

 ment with normal urine should always be made. 



Add to the urine in a test-tube some nitric acid and heat 

 to boiling: an odor resembling that of bitter almonds becomes 

 perceptible (formation of volatile ortho-nitrophenol) ; when 

 perfectly cold add bromine-water to part of the liquid: more 



